TRT - Organization

Principles for the Organization of the Transportation Research
Thesaurus

Introduction

The Transportation Research Thesaurus (TRT) is a standard for the
indexing of transportation concepts and topics. It was developed
under the National Cooperative Highway Research Program (NCHRP),
Projects 20-32 and 20-32(2), administered by the Transportation Research
Board (TRB). This Principles document is intended as a policy
statement for specific practices within the organization and development
of the TRT. It is intended to provide scope and structure to those
involved in the development of the thesaurus.

Foundation

The TRT was originally developed to serve as an indexing tool for
the Transportation Research Thesaurus (TRIS). As such, it was
created as a multimodal thesaurus with an emphasis on highways.

The TRT conforms to the National Information Standards
Organization’s American National Standard (ANSI/NISO) Z39.19-2005,
entitled Guidelines for the Construction, Format, and
Management of Monolingual Controlled Vocabularies.

The TRT has already been defined in detail in the Transportation
Research Thesaurus and User’s Guide (NCHRP 450). The
Principles document reviews some of the information contained in the
NCHRP report, and in ANSI/NISO Z39.19-2005, but it is focused primarily
on establishing policies and procedures for the review and update of the
TRT. For additional information on the structure, history, and
philosophy behind the creation of the TRT, please refer to the documents
listed above.

Scope

The TRT is being expanded to contain all subjects relating to the
general field of transportation, including air, land, sea, and space
modes.

The TRT does not generally include proper names. This
includes formal names of government agencies, organizations, persons, or
places. The one exception to this is instances in which the proper
name has entered into common usage (e.g., Terzaghi's rule). It is
strongly recommended that a standard authority list be used for all
proper names. Two possible lists are the Library of Congress
Authority File and the United States Board of Geographic Names.

Structure

The TRT is organized into a set of 21 hierarchies, called
facets. Each facet consists of one Top Term that represents a
principle concept within the TRT. Below each Top Term are terms
that are both closely related and subordinate to it.

Terms within the TRT are labeled using a notation system.
The system identifies the Top Term using a capital letter, and uses
lower case letters to indicate subordinate levels in the hierarchy,
resulting in a unique notation for each term in the thesaurus.

Figure 1: Example of the TRT Structure

Terms within the TRT are linked through their semantic
relationships to one another. The semantic connection between
terms can generally be defined as one of three relationship types:
hierarchical, equivalent, or associative.

Hierarchical relationships

Hierarchical relationships are based on levels of superordination
and subordination, where subordinate terms represent members or parts of
the superordinate term. Hierarchical relationships are expressed
as broader terms (BT) and narrower terms (NT).

Figure 2: Example of the TRT hierarchical relationship

Underground structures are a type of Specialized
facility, while Underground parking garages in turn are a type
of Underground structure.

Equivalence relationships

It is not uncommon for one concept to be represented by several
different terms. Because of this, within the TRT, one preferred
term is selected for each concept. Terms that are synonyms or
near-synonyms to the preferred term, those that have variant spellings,
or those that represent a focus that is too narrow for the scope of the
TRT are linked to the preferred term.

In the full display of the preferred term, these
non-preferred terms are referred to as Use For terms (UF).

Figure 3: Example of the TRT non-preferred relationship

Ground transportation is the preferred term, and both Land
transportation and Surface transportation are non-preferred
terms for this concept. Any searches that are performed on either
of these terms will refer the searcher to Ground
transportation.

Figure 4: Another example of the TRT non-preferred relationship

Given the TRT’s focus as a transportation resource, the
addition of Taverns as a preferred term, would be a far too
specific term. However, it is possible that indexers or
researchers might search for the term. Therefore, it is added as a
non-preferred term within the broader topic of Drinking
establishments, which is an established term within the TRT.

Associative relationships

Associative relationships exist between terms that are neither
hierarchical nor equivalent, but are nevertheless semantically related
to one another.

Within the TRT, there are two types of associative relationships:
related terms, and cross-references.

Related terms

Related terms (RT) are terms that are siblings within the same
branch of the hierarchy, and which therefore, possess the same
superordinate term.

Cross-references

Although they have different parent terms, the topics of Vehicle
operations, and Occupant protection devices relate to the
concept of Vehicle safety, and are therefore added to that term
as cross-references. Note that although they may be of interest in
the topic of Vehicle safety, Vehicle operations and Occupant
protection devices are not related to one another. Therefore,
there are no cross-references between these two terms.

Term collection

Terms considered for inclusion into the TRT are collected from a
wide variety of sources. Broadly, they are collected based on
literary warrant, user warrant, and organizational warrant.

Literary warrant

Literary warrant involves examining the vocabulary of the
literature, documents, and other source material of the thesaurus’
subject area to determine terms to be added to the thesaurus. In
the case of the TRT, this need is met through the regular Transportation
Research Information Service (TRIS)and National Transportation
Library (NTL) Digital Repository and library catalog reports of
uncontrolled terms and keywords used in records of those databases.

User warrant

User warrant is determined by examining the search terms and
phrases frequently used in requests from users to an information storage
and retrieval system. Both TRIS and the NTL provide periodic
reports to the TRT selection team to track such searches.

Organizational warrant

Usually organizational warrant involves identifying the terms
preferred by the organization or organizations that will use the
vocabulary. As the TRT is an international standard, identifying
term preference for all organizations connected to transportation would
be impractical. Instead, the TRT selection team and the
Transportation Research Board’s TRT Subcommittee have chosen to
view the transportation community as a whole as a de facto
organization. As such, suggested terms are being actively
solicited from that group.

Term selection

Precoordinated and postcoordinated terms

A precoordinated term is one that combines multiple concepts into
a compound term in order to indicate a specific concept more
accurately. Postcoordinated terms are those that are combined at
searching by the vocabulary’s user, usually involving a
combination of Boolean operators.

Terms selected and arranged so as to allow easy postcoordination
are preferred where possible as precoordinated terms can increase the
size and complexity of a vocabulary. There are, however, some
instances in which precoordinated terms should be retained:

When a phrase occurs frequently within the
literature/vocabulary
Example:
Per se laws
Kiss and ride
Eminent domain

It is possible for some concepts to belong to more than one
category. This is known as polyhierarchy. The TRT’s
notational organization does not allow for polyhierarchy.
Therefore, when a term may reasonably be considered a member of more
than one branch of the thesaurus, it should be placed under the branch
in which it most frequently appears in literary, user, and
organizational warrant. Cross-references should be added pointing
from the other possible branches towards the preferred term.

Form of term

The form of the term should be decided by literary, user, and
organizational warrant. The most common spelling of the word,
including use of hyphens and apostrophes, should be selected. When
variant spellings and punctuation occur, non-preferred heading should be
created for them.

Natural language order

Use natural language order, also known as direct order, for the
entry of terms. If it is considered necessary for alphabetical
listings, non-preferred headings may be included for the indirect form
of the term.

Plural vs. singular form of term

Below are explanations and examples to describe when a term
should take a plural form and when it should take a singular form.
Please note, however, that there may be instances in which both the
singular and plural form of the name are needed in the TRT (for example,
if they represent different concepts, or are used to distinguish process
from product). In those cases, the terms should be assigned either
qualifiers or scope notes, as appropriate.

Plural form

Terms in the TRT should be made plural in the following case:
a) Count nouns – terms about which the question “How
many?” can be asked, but about which the question “How
much?” cannot be asked.

Example:
Pipeline companies
Composite pavements

Singular form

Terms in the TRT should be made singular in the following cases:
a) Noncount nouns – terms about which the question
“How much?” can be asked, but about which the question
“How many?” cannot be asked.

Example:
Electric power supply
Econocrete

b) Abstract concepts – these include activities or
processes, properties or states, and disciplines.

Acronyms and abbreviations

All terms should be entered in their full form. Any
acronyms or abbreviations that widely appear in common use may be
included as non-preferred terms. When an acronym or abbreviation
is entered, it should be done so without periods (e.g., DUI rather than
D.U.I.)

Capitalization

The first letter of every term should be capitalized, as should
all proper names. Further capitalization may be added if a term
includes capitalization in common use, e.g., pH value

American form

The American spelling and usage of a term should be used.
If it is considered useful for search purposes, non-preferred headings
may be included for the non-American form of a term (e.g., Armored
vehicles rather than Armoured vehicles).

Notes

Scope notes

Scope notes are intended to explain the scope and meaning of a
term, as well as to refer the searcher to other sections of the TRT when
necessary. Scope notes are to be used for ambiguous terms only,
and are not to provide standard definitions (see section 7.2 for
explanation of definitions).

Example:

Admixtures
Scope note: Material other than water,
aggregates or cement added to concrete during mixing

When a scope note refers to another term in the TRT, a reciprocal
scope note should be included in that term.

Definitions

Definitions are intended to provide the searcher with the
standard definition of the term. It is also expected that
thesaurus users will examine the placement of the term within the
hierarchy to further illustrate its intended use and meaning.

Editorial notes

Editorial notes contain any documentation, research, or comments
from those involved in maintaining the TRT. The notes are visible
only to those with access to the TRT editing software.